Organopolysiloxanes having a silanol group and process of making them

Abstract: Novel organopolysiloxanes having one silanol group within a molecule and the method for manufacturing them at high purity and high yield. The organopolysiloxanes having a silanol group are expressed by the formula (1) below: wherein R¹ s a monovalent organic group with 1 to 8 carbon atoms, each of R², R³ and R⁴ is a monovalent organic group with 1 to 8 carbon atoms or a siloxyl group expressed by -OSiR⁵R⁶R⁷ wherein R⁵, R⁶, and R⁷ are independently substituted or unsubstituted monovalent hydrocarbon groups with 1 to 8 carbon atoms, Y is a hydrogen atom, a halogen atom, or a monovalent organic group of 1 to 12 carbon atoms, n is an integer of from 0 to 12, and a is either 0 or 1, with the proviso that the grouping Y-(CH₂) n -Si is not H-Si, CH₃-Si or a hydrolyzable silyl group.

Description: This invention relates to organopolysiloxanes having a silanol group and a process of making them. Organopolysiloxanes having silanol groups at both molecular terminals expressed by the chemical formula below, are conventionally known: These compounds are widely employed in many fields, for example, as a room temperature curable liquid silicone rubber. Further, silanols expressed by the chemical formulae below are known as compounds having one silanol group in a molecule: (CH 3 ) 3 SiOH, and However, these silanols undergo a condensation through the mechanism (A) shown below and, as a result, high purity organopolysiloxanes may be obtained by distillation but only at a disadvantageously low yield: ≡Si-OH + OH-Si≡ → ≡Si-O-Si≡ + H 2 O On the other hand, an organopolysiloxane containing one silanol group at one molecular end, expressed as below, is of interest: This compound may be synthesized by the living polymerization of cyclic organopolysiloxanes with silanols, as shown by the formula below, which is described in, for example, European Patent Specification, EP-A-0508490. However, a complicated process is required to prepare such a silanol terminated compound with a high precision by this method and it also requires a high degree of technology. In addition; the importance of compounds having one silanol group per molecule has recently been recognized; therefore the development of methods which enable one to prepare them easily at high purity and high yield is strongly in demand. EP 0544 257 A2 discloses triorganosiloxydiphenylsilanols of the following general formula wherein C 6 H 5 designates the phenyl radical and each of the radicals R is individually selected from substituted and unsubstituted monovalent hydrocarbon radicals. Said silicone compounds shall be useful as plastizisers for silicone rubbers. It is the object of the present invention to provide alternative organopolysiloxanes with one silanol group, said siloxanes having improved properties such as a reduced tendency towards condensation during preparation or isolation, and to provide a more simple and advantageous manufacturing process for said organopolysiloxanes in high purity and high yield. This object was solved by the organopolysiloxanes having a silanol group, expressed by the formula (I) below, and the manufacturing method thereof: wherein each of R 2 , R 3 , and R 4 is independently either a substituted or unsubstituted monovalent hydrocarbon group of 1 to 8 carbon atoms or a siloxyl group of the formula -OSiR 5 R 6 R 7 , wherein R 5 , R 6 , and R 7 are substituted or unsubstituted monovalent hydrocarbon groups with 1 to 8 carbon atoms, Y is either a hydrogen atom, a halogen atom, or a monovalent organic group with 1 to 12 carbon atoms, and n is an integer of from 0 to 12, preferably 0 to 3. However, the group, Y-(CH 2 ) n -Si, does not include H-Si, CH 3 -Si or hydrolyzable silyl groups. Examples of hydrocarbon groups with 1 to 8 carbon atoms for R 2 , R 3 , R 4 , R 5 , R 6 , and R 7 are: alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group; cycloalkyl groups such as a cyclopentyl group and a cyclohexyl group; aryl groups such as a phenyl group; aralkyl groups such as a benzyl group; alkenyl groups such as a vinyl group, and an allyl group; and hydrocarbon groups substituted with halogens or cyano, such as a chloromethyl group, a 3,3,3-trifluoropropyl group, and a 2-cyanoethyl group. Examples of siloxyl groups expressed by -OSiR 5 R 6 R 7 in R 2 , R 3 , and R 4 are a trimethyl siloxyl group, an ethyl dimethyl siloxyl group, a 3,3,3-trifluoropropyl dimethyl siloxyl group, and a 2-cyanoethyl dimethyl siloxyl group. Each of R 2 , R 3 , R 4 , R 5 , R 6 , and R 7 may be the same or different; however, they are desirably methyl groups due to the ease in synthesis. Further, Y is either a hydrogen atom, a halogen atom, or a monovalent organic group with 1 to 12 carbon atoms, and it may be appropriately selected depending upon the characteristics desired for the organopolysiloxane having a silanol group of this invention. For example, when Y is a hydrogen atom or a halogen atom, the organopolysiloxane will contain a linear alkyl group or a halogen substituted linear alkyl group, respectively. Particular examples of Y as a monovalent organic group with 1 to 12 numbers of carbon atoms are: the saturated hydrocarbon groups such as linear alkyls, branched alkyls, and cyclic alkyls; the unsaturated hydrocarbon groups such as alkenyl groups and alkynyl groups; and the aromatic hydrocarbon groups such as a phenyl group and a naphthyl group. Further, a part, or all, of the hydrogen atoms in these organic groups may be substituted by halogen atoms, (meth)acryloyl groups, cyano groups, and nitro groups, or Y, as a whole, may be one of these groups. Also, the organic groups may also contain hetero atoms such as nitrogen, oxygen and sulfur, e.g., as amine, amide, hydroxy, ether, thiol or thiolether groups. However, Y must be stable when in the form of an organohalosilane, expressed by the formula below, from the performance viewpoint during the manufacturing method of this invention: Y―(CH 2 ) n ―Si―X 3 wherein X, Y, and n are the same as described in formula (1). Considering this point, a monovalent organic group Y is preferably either a (meth)acryloyl group, a vinyl group, a halogen substituted hydrocarbon group or a cyano group. Among the halogen substituted hydrocarbon groups, perfluoroalkyl groups such as a trifluoromethyl group, a nonafluorobutyl group, and a heptadecafluorooctyl group are particularly preferred. The organopolysiloxane having a silanol group of this invention is prepared by the following synthetic reactions, expressed by the equations (B) and (C). wherein the variables are as defined above. In the reaction (B), the elimination of hydrogen halide takes place between organohalosilane expressed by the formula (2) and the silanols expressed by the formula (3) in order to prepare a monohalo-polysiloxane. Then the monohalo-polysiloxane is hydrolyzed by the reaction (C) to obtain the organopolysiloxane having a silanol group, expressed by formula (1), of this invention, Y―(CH 2 ) n ―Si―X 3 The synthesis of the compound expressed by the formula (1) from the compounds expressed by the formulae (2) and (3) is new. However, the elementary reactions (B), dehydrohalogenation, and hydrolysis (C) are already well-known in general. Therefore, utilization of solvents, catalysts, agents for the hydrogen halide elimination, and stabilizers, and the reaction conditions such as reaction temperature, reaction time, and purification methods would have been known to one of ordinary skill in the art, and are not particularly limited to specifics during the performance of these reactions. The selectivity in the elimination of the hydrogen halide in reaction (B) is high, and the reactivity of the Si-X bond in the compound (2) reduces as the reaction proceeds due to the effect of the increased stearic hindrance at the vicinity of the Si-X bond by addition of the triorganosiloxy groups. Therefore, if the progress of the hydrogen halide elimination is expressed by the compound expressed by the formula (4), the rate of the reaction between the Si-X bond in the formula (4) and the compound (3) is in the order of (b = 3) > (b = 2) >> (b = 1): wherein X, R 2 , R 3 , R 4 , Y, and n are the same as described in the chemical formula (1) and b is either 1, 2, or 3. Considering the above, it was discovered that controlling the molar ratio of the compounds of the formulae (2) and (3), respectively, to be substantially at 1/2 or about 1/2 results in selectivity to the intended product of the compound (1). When this molar ratio is significantly smaller than 1/2, the completely triorganosiloxyl substituted product, expressed by the formula (5) will be more readily produced: This compound possesses similar characteristics, especially a boiling point, to those of the compound (1) of the intended product of this invention. Therefore, distillation of the product mixture will not separate them and the compound (5) will remain in the final product as an impurity. On the other hand, a larger molar ratio than the 1/2 level will lower the yield by leaving unreacted the portion of the compound (4), in which b is 2 or 3. Further, the unreacted portion of the compound will produce multiple numbers of silanol groups at the next reaction stage, hydrolysis. These silanol groups will have a lower stearic hindrance; therefore, they will condense to form oil-like or gel-like products. This will also reduce the yield. It is also obvious that the contamination of water must be avoided in the reaction expressed by (B). For example, the silanols expressed by the formula (4) may produce water during storage by condensation as in reaction (A). The water produced by such condensation will react with the Si-X bond in the organohalosilane, expressed by the formula (2). Therefore, it will disturb the molar ratio balance of compounds (2) and (3) within the reaction system and cause a lowering in yield. Therefore, it is desirable to perform a dehydration treatment by using anhydrous sodium sulfate, anhydrous magnesium sulfate, anhydrous potassium chloride, silica gel, or molecular sieves, and more preferably a further distillation for purification, prior to the use of the silanols expressed by the formula (3). It is also desirable to ventilate the inside of the reaction vessel with dry nitrogen gas, or to dehydrate reaction reagents prior to the use, for the same reason. On the other hand, the silanol group within the compounds of this invention, expressed by the chemical formula (1), are restricted from condensation with each other due to the stearic hindrance. Therefore, the compounds of formula (1) are stable towards heating associated with, for example, distillation. This indicates that the bulkier the groups of R 2 , R 3 , R 4 , and Y-(CH 2 ) n in the said compound (1) of this invention, the better is the stability in the protection towards condensation. Based on the above, organochlorosilanes which are easily accessible and easily handled are desirably used as the organohalosilane expressed by the formula (2) in this invention. Examples of such organopolysiloxanes are: ethyl trichlorosilane, phenyl trichlorosilane, vinyl trichlorosilane, n-hexyl trichlorosilane, n-octyl trichlorosilane, n-decyl trichlorosilane, n-dodecyl trichlorosilane, 3-(meth)acryloyloxy propyl trichlorosilane, 3-[2-(meth)acryloyloxy ethoxy] propyl trichlorosilane, 11-(meth)acryloyloxy undecyl trichlorosilane, allyl trichlorosilane, 5-hexenyl trichlorosilane, 9-decenyl trichlorosilane, chloromethyl trichlorosilane, 3-chloropropyl trichlorosilane, 3-bromopropyl trichlorosilane 10-bromodecyl trichlorosilane, 3,3,3-trifluoropropyl trichiorosilane, 2-(nonafluorobutyl) ethyl trichlorosilane, 2-(heptadecafluorooctyl) ethyl trichlorosilane, and 2-cyanoethyl trichlorosilane; ethyl methyl dichlorosilane, phenyl methyl dichlorosilane, vinyl methyl dichlorosilane, n-hexyl methyl dichlorosilane, n-octyl methyl dichlorosilane, n-decyl methyl dichlorosilane, n-dodecyl methyl dichlorosilane, 3-(meth)acryloyloxy propyl methyl dichlorosilane, 3-[2-(meth)acryloyloxy ethoxy] propyl methyl dichlorosilane, 11-(meth)acryloyloxy undecyl methyl dichlorosilane, allyl methyl dichlorosilane, 5-hexenyl methyl dichlorosilane, 9-decenyl methyl dichlorosilane, chloromethyl methyl dichlorosilane, 3-chloropropyl methyl dichlorosilane, 3-bromopropyl methyl dichlorosilane, 10-bromodecyl methyl dichlorosilane, 3,3,3-trifluoropropyl methyl dichlorosilane, 2-(nonafluorobutyl) ethyl methyl dichlorosilane, 2-(heptadecafluorooctyl) ethyl methyl dichlorosilane, and 2-cyanoethyl methyl dichlorosilane. As the silanols expressed by the formula (3), examples such as trimethyl silanol, dimethyl trimethyl siloxy silanol, methyl bis(trimethyl siloxy) silanol, and tris(trimethyl siloxy) silanol are particularly preferred. The organopolysiloxane having a silanol group in this invention is a novel compound having one silanol group, which silanol group has little or no condensation, within a molecule. The selection of certain organic groups on the organopolysiloxane will even further increase its industrial value. Further, according to the manufacturing method of this invention, the organopolysiloxane having a silanol group of this invention may be manufactured easily at high purity and high yield, without requiring special instruments and techniques. In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and percentages are by weight. Description of the Drawings Figure 1 is an IR spectrum presenting an analytical result of the organic silicon compound of Example 1. Figure 2 is an 1 H-NMR spectrum presenting an analytical result of the organic silicon compound of Example 1. Figure 3 is an IR spectrum presenting an analytical result of the organic silicon compound of Example 2. Figure 4 is an 1 H-NMR spectrum presenting an analytical result of the organic silicon compound of Example 2. EXAMPLES Next, this invention will be explained further in detail by using Examples. However, the invention is not limited to these Examples. Example 1 42.4 g (0.2 mol) of 3-chloropropyl trichlorosilane, 62.6 g (0.62 mol) of triethyl amine, and 250 ml of toluene were placed within a one liter capacity flask equipped with a dropping funnel, a condenser, a thermometer, and a stirrer, and the mixture was cooled to 10 °C while stirring. Then, 36.0 g (0.4 mol) of trimethyl silanol, preliminarily dried, was added slowly drop by drop and the mixture was stirred at 10 °C for an hour. Further, 100 ml of 0.5 N hydrochloric acid was added and stirred at room temperature for another hour, in order to dissolve produced amine hydrochloride as well as to hydrolyze the Si-Cl bonds. The obtained reaction mixture was separated, and the organic layer was washed with saturated salt water until neutralized. Then, the solvent was eliminated by the distillation under reduced pressure after drying by anhydrous sodium sulfate. The obtained distillation residue was purified using a rectifying column and a colorless and transparent liquid with a boiling point of 95 to 97 °C (3 mmHg) was obtained. This liquid was tested by IR, 1 H-NMR, and MS and identified by the elemental analysis. As a result, it was confirmed to be a compound expressed by the formula (6) below; 41.4 g of the compound was obtained at 68.9 % yield. The analytical results are shown below, as well as IR and 1 H-NMR spectra in Figures 1 and 2, respectively. Analytical Results IR (cm -1 ): 3420 (O-H) 2960 (C-H) 1250 (Si-C) 1070 (Si-O) 710 (C-Cl) 1 H-NMR: δ (ppm) 0.13 (s, 18H, Si-CH 3 ) Solvent: CCl 4 0.4 - 0.8 (m, 2H, C-CH 2 -Si) 1.5 - 2.1 (m, 2H, C-CH 2 -C) 2.7 (s, 1H, Si-OH) 3.4 (t, 2H, Cl-CH 2 -C) MS (Mass Spectroscopy): M + (m/e): 301 Elemental Analysis % (Calculated value) C 36.11 (35.94) H 8.29 ( 8.32) Cl 11.69 (11.81) Si 28.07 (27.95) Example 2 52.3 g (0.2 mol) of 3-methacryloyloxy propyl trichlorosilane, 62.6 g (0.62 mol) of triethyl amine, 100 mg of 2,2'-methylene bis(4-ethyl-6-tert-butyl phenol), and 250 ml of toluene were placed in the similar flask as used in Example 1. A colorless and transparent liquid with a boiling point of 97 to 100 °C (5 x 10 -3 Torr) was obtained by the similar method described in Example 1 including drop by drop addition of the 36.0 g (0.4 mol) of trimethyl silanol. This liquid was tested by IR, 1 H-NMR, and MS and identified by the elemental analysis. As a result, it was confirmed to be a compound expressed by the formula (7) below: 50.1 g of the compound was obtained at 71.6 % yield. The analytical results are shown below, as well as IR and 1 H-NMR spectra in Figures 3 and 4, respectively. Analytical Results IR (cm -1 ): 3480 (O-H) 3090 (CH 2 =C) 2960 (C-H) 1720, 1700 (C=O) 1250 (Si-C) 1060 (C-O, Si-O) 1 H-NMR: δ (ppm) 0.13 (s, 18H, Si-CH 3 ) Solvent: CCl 4 0.4 - 0.8 (m, 2H, C-CH 2 -Si) 1.5 - 2.1 (m, 5H, C-CH 2 -C, C=C-CH 3 ) 3.8 (s, 1H, Si-OH) 4.1 (t, 2H, COO-CH 2 -C) 5.4 (m, 1H, H-C=C) 6.0 (m, 1H, H-C=C) MS (Mass Spectroscopy): M + (m/e): 350 Elemental Analysis % (Calculated value) C 44.71 (44.57) H 8.44 ( 8.57) Si 24.04 (24.00) Example 3 55.1 g (0.2 mol) of n-decyl trichlorosilane, 62.6 g (0.62 mol) of triethyl amine, and 250 ml of toluene were placed in the similar flask as used in Example 1. A colorless and transparent liquid with a boiling point of 118 to 120 °C (5 x 10 -3 Torr) was obtained by the similar method described in Example 1, including drop by drop addition of the 36.0 g (0.4 mol) of trimethyl silanol. This liquid was identified to be a compound expressed by the formula (8) below: 54.7 g of the compound was obtained at 75.2 % yield. Example 4 116.3 g (0.2 mol) of 2-(heptadecafluorooctyl) ethyl trichlorosilane, 62.6 g (0.62 mol) of triethyl amine, and 250 ml of α, α, α, α', α', α'-hexafluoro-m-xylene were placed in the similar flask as used in Example 1. A colorless and transparent liquid with a boiling point of 123 to 126 °C (3 mmHg) was obtained by the similar method described in Example 1, including drop by drop addition of the 36.0 g (0.4 mol) of trimethyl silanol. This liquid was identified to be a compound expressed by the formula (10) below: 89.9 g of the compound was obtained at 67.0 % yield. Example 5 43.5 g (0.2 mol) of 5-hexenyl trichlorosilane, 62.6 g (0.62 mol) of triethyl amine, and 250 ml of toluene were placed in the similar flask as used in Example 1. A colorless and transparent liquid with a boiling point of 121 to 122 °C (5 mmHg) was obtained by the similar method described in Example 1, including drop by drop addition of the 36.0 g (0.4 mol) of trimethyl silanol. This liquid was identified to be a compound expressed by the formula (11) below: 40.1 g of the compound was obtained at 65.5 % yield. Example 6 37.7 g (0.2 mol) of cyanoethyl trichlorosilane, 62.6 g (0.62 mol) of triethyl amine, and 250 ml of toluene were placed in the similar flask as used in Example 1. A colorless and transparent liquid with a boiling point of 134 to 135 °C (3 mmHg) was obtained by the similar method described in Example 1, including drop by drop addition of the 36.0 g (0.4 mol) of trimethyl silanol. This liquid was identified to be a compound expressed by the formula (12) below: 30.7 g of the compound was obtained at 55.4 % yield. Comparative Example 1 The reaction was carried out by exactly the same method described in Example 2, except that 45.0 g (0.5 mol) of trimethyl silanol was added drop by drop. As a result, the compound expressed by the formula (13) below was produced as a by-product and the purification by distillation resulted in a mixture of the compounds (7) and (13), the ratio being about 50:50 by weight. Comparative Example 2 The reaction was carried out by exactly the same method described in Example 2, except that 27.0 g (0.3 mol) of trimethyl silanol was added drop by drop. A composition expressed by the formula (7) was obtained; however, there was much residue after distillation. As a result, only 22.7 g of the product was obtained and the yield was only 32.4%.

Claims: Organopolysiloxanes having a silanol group of the general formula (1): wherein each of R 2 , R 3 and R 4 is independently either a substituted or unsubstituted monovalent hydrocarbon group of 1 to 8 carbon atoms or a siloxyl group of the formula -OSiR 5 R 6 R 7 wherein R 5 , R 6 , and R 7 are independently substituted or unsubstituted monovalent hydrocarbon groups with 1 to 8 carbon atoms, Y is either a hydrogen atom, a halogen atom, or a monovalent organic group of 1 to 12 carbon atoms, and n is an integer of from 0 to 12, with the proviso that the grouping Y-(CH 2 ) n -Si is not H-Si, CH 3 -Si or a hydrolyzable silyl group. Organopolysiloxanes of claim 1, wherein the monovalent hydrocarbon groups in R 2 - R 7 are alkyl groups, cycloalkyl groups, alkenyl groups, a phenyl group or a benzyl group, each of which is, optionally, substituted by halogenes or cyano groups. Organopolysiloxanes of claim 1, wherein at least one of R 2 , R 3 , and R 4 is a siloxyl group selected from trimethyl siloxyl, ethyl dimethyl siloxyl, 3,3,3-trifluoropropyl dimethyl siloxyl and cyanoethyl dimethylsiloxyl. Organopolysiloxanes of claim 1, wherein each of R 2 , R 3 , and R 4 is methyl. Organopolysiloxanes of claim 1, wherein Y is a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, a phenyl group, an aromatic hydrocarbon group, each group being optionally substituted by halogen atoms, (meth)acryloyl groups, cyano groups or nitro groups, and, optionally, wherein the group is interrupted by nitrogen, oxygen or sulfur atoms. Organopolysiloxanes of claim 1, wherein Y is a (meth)acryloyl group, a vinyl group, a halogen-substituted hydrocarbon group or a cyano group. Organopolysiloxanes of claim 1, wherein Y is a perfluoroalkyl group. The method for the preparation of the oganopolysiloxanes having a silanol group of claims 1 to 7, comprising reacting an organohalosilane expressed by the formula (2) below and a silanol expressed by the formula (3) below in a molar ratio of [compound (2)]/[compound (3)] substantially equal to 1/2, then hydrolyzing the obtained reaction product: Y―(CH 2 ) n ―Si―X 3 wherein X in the formula (2) is a halogen atom, and Y and n in the formula (2) and R 2 , R 3 and R 4 in the formula (3) are the same as described in claim 1. The method of claim 8, wherein the silanol of the formula (3) is dried before the reaction with the organohalosilane of formula (2). The method of claim 9, wherein the silanol is dried by treating said silanol with anhydrous sodium sulfate, anhydrous magnesium sulfate, anhydrous potassium chloride, silica gel or a molecular sieve or by distilling said silanol.

Inventors: ICHINOHE SHOJI, MORIOKA SHINICHI, SUZUKI NOBUYUKI, TOSHIO YAMAZAKI, ICHINOHE, SHOJI, MORIOKA, SHINICHI, SUZUKI, NOBUYUKI, TOSHIO, YAMAZAKI
Applicants: SHINETSU CHEMICAL CO, SHIN-ETSU CHEMICAL CO., LTD.
Application year: 1994
Main classification: C07F7
IPC codes: C07F7, C08G77